Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

The pesticide concentrations appear quite low. However, children are more sensitive to these chemicals than adults. The EPA advises that daycare centers and schools adopt pest-management practices that reduce sources of food, water and shelter for pests.

The agency said these precautions are usually cheaper and safer than pesticides. Roughly 13 million children attend daycare each day in the United States. In the first nationwide study of environmental safety in U.S. daycare centers, researchers analyzed 168 sites across the United States for 39 pesticides.

Field technicians spent about four months in 2001 wiping samples from indoor surfaces, such as floors, desks and tables, and scraping up soil from outdoor play areas from all the centers. Center directors were also quizzed about cleaning practices and pesticide use. At least one pesticide was found in every daycare center studied. Pesticides were used up to 107 times annually.

A large variety of pesticides were used, with centers employing up to 10 different kinds. The most commonly found pesticides were chlorpyrifos, diazinon and permethrin. Chlorpyrifos and diazinon are organophosphates, which kill insects by disrupting their brains and nervous systems and can also harm the brains and nervous systems of animals and humans. Permethrin attacks the nervous system and is possibly a carcinogen. It is a type of pyrethroid, which are similar to the pesticide pyrethrum naturally produced by chrysanthemums.

Since the study was first conducted, chlorpyrifos and diazinon were banned by the EPA for use in daycare centers, homes and nearly all indoor locales. Levels the researchers found of permethrin "are many times lower" than those the EPA have already deemed acceptable, researcher Nicolle Tulve, a research scientist with the EPA's National Exposure Research Laboratory in Research Triangle Park, N.C., told LiveScience.

Tulve and her colleagues reported their findings in the Oct. 15 issue of the journal Environmental Science & Technology.